Corrects for group delay distortions introduced by the satellite transponder

Easy software upgrades for extra features

Web Browser control and via easy-to-use front panel, SNMP, RS-232 or RS-485 remote control or Telnet

Ericsson SM6635 Satellite Modulator with DVB-S2 CCM, VCM and PREKOR

The rapid rise of bit-rate intensive high definition television and the continuing need for costeffective transmission over satellite is accelerating the change to more efficient transmission technology. The DVB-S2 standard is at the forefront of providing the means to fulfilling this requirement.

Operators running distribution of cable and digital terrestrial multiplexes over satellite also seek new ways to save transmission costs The DVB-S2 Variable Coding and Modulation (VCM) mode option provided by the SM6635 answers these requirements. By further utilizing Ericsson’s unique Prekor™ Dynamic Pre-correction System the SM6635 can deliver up to twice the data-rate previously capable with legacy DVB-S distribution techniques.

Sample Configuration

SM6635 Overview

The SM6635 supports all DVB standard modulation modes (DVB-S, DVB-DSNG, DVB-S2) making this well specified product extremely flexible and capable of performing in all types of system architectures.

Variable Symbol Rate

The SM6635's wide symbol rate range from 0.2 to 66 Msyms makes it suitable for all applications from low bit-rate DSNG transmissions to high data rate IP backbone applications.

High Quality L-band Output

The SM6635 follows the high spec design philosophy through to its L-band output stage by offering the highest possible transmission quality. The SM6635 offers a number of signal quality improvement tools such as group delay correction through PREKOR and digitally generated cable tilt correction to ensure that the received satellite signal is free from distortions.

Full Set of Control Methods

The SM6635 incorporates an easy to use web browser control interface as well as full control through SNMP, RS232, RS485 and Telnet sessions. For local control the SM6620 also has a simple to operate front panel control.

About DVB-S2

DVB-S2 is the next-generation standard for satellite broadcasting offering up to a 30% increase in throughput or a 1.5 to 2dB increase in link margin bringing 8PSK within the reach of consumer sized dishes. The combination of savings in bit-rate from Advanced Video Coding and the increased efficiency of DVB-S2 makes the transmission of HD video a real and financially attractive reality.

Example DVB-S2 Configuration for Equivalent Failure Point to DVB-S

About DVB-S2 VCM Dual Transport stream

DVB-S2 VCM mode allows multiple, separate transport streams to be timedivision multiplexed into one RF satellite carrier. Because single carrier per satellite transponder transmission is both more power and bandwidth efficient than multi-carrier per transponder transmission this DVB-S2 mode achieves significant throughput gains that can be particularly valuable to DTT and cable distribution over satellite.

About PREKKOR

Ericsson’s unique PREKOR option ensures optimum performance from the satellite link for those who wish to get the most from their system.

Applications such as satellite distribution of TV to multiple headends and Internet backbone applications are particularly suited to the implementation of PREKOR. In these applications cost per bit is of primary consideration. The improvement in the satellite link margin that PREKOR gives can result in an increase in data capacity of up to 7% for QPSK, 22% for a DVB-DSNG 8PSK system and up to 55% for a 16QAM system.

PREKOR is of benefit to users employing satellite modulation in a single carrier per transponder mode. In this mode maximum power efficiency of the satellite link is achieved by operating the satellite transponder at saturation. The dynamic pre-correction technology of PREKOR corrects for group delay and removes the phase and magnitude non-linear distortions introduced by operating the transponder at saturation. The higher order modulations of 8PSK, 16QAM and 16APSK are particularly sensitive to these distortions and so PREKOR can yield large improvements in the satellite link margin.

By combining PREKOR and DVB-S2 modulation with MPEG-4AVC compression technology, the satellite distribution can be made highly efficient enabling more services per transponder than any other open system available today.

Integrating PREKOR into an earth station generally has little effect on the system architecture. PREKOR is housed in the SM6625 satellite modulator, which provides industry standard interfaces. When required to operate with transponders having no AGC, a beacon receiver may be required in order to adjust the correction process automatically during rain fades. PREKOR is configured on installation for use with a particular path. There is no need to be able to see the downlink during operation, and during installation it is possible to extend control of the modulator to the receive site via the Internet. The ability to store numerous configurations allows its use in complex redundancy systems.

PREKOR requires no special equipment at the receive station. Any receiver compliant with EN 300 421, EN 301 210 or EN 302 307 such as the TT1260, may be used.

PREKOR Specifications

Satellite Channel Normalized

small signal gain:

4.0 dB maximum

Phase correction range:

0 - 90°

Phase polarity:

Lag or lead with increasing amplitude

Group delay correction range:

0 - 200 ns at the transponder band edge

Group delay correction shape:

Parabolic +nth order term, n=2-7

Symbol rate range:

1 - 48 Msyms 0.2 - 66 Msyms (option)

Transmit/receive roll-off factor

25%

NOTE: Some DVB receivers operate with 0.35 roll-off. Such a mismatch does not introduce significant degradation.

Earth Station Requirements

In order to ensure that PREKOR can deliver the best possible performance, it is important that the overall performance of both uplink and downlink earth stations meet certain minimum requirements. These requirements will depend upon individual circumstances. Please contact Ericsson for further information.

Improvements due to PREKOR

Pre-correction gain may be specified in two ways:

As a system threshold improvement in dB for a fixed user bit-rate.

As a percentage increase in the user bit-rate for a fixed system threshold. This assumes that an appropriate code-rate is available.

Ni = Non-linear improvement, Gi = Group delay improvement

The total gain in system performance is not achieved from any single feature of the system. A large system gain is normally the result of the combination of the individual improvements to the system. The table above gives a maximum expectation of system gain for a TWT based transponder in conjunction with a TWT based HPA driven at 3 dB OBO and a typical level of uplink noise.